July 3, 1913] 



NATURE 



46: 



of Agriculture has made a grant of 3100/. out of the 

 Development Fund, and has also promised an annual 

 maim, nance grant of 2500/. from the same source. 

 These grants are made on the "pound for pound'' 

 principle, i.e. they are given subject to an equal 

 amount being raised from other sources. The Society 

 for the Extension of the Rothamsted Experiments was 

 founded for the purpose of collecting subscriptions, 

 and is now making a further appeal. Subscriptions 

 and donations should be sent to the secretary, the 

 Rothamsted Experiment Station, Harpenden. 



It is hoped to raise 6000/. as the centenary fund, 

 and thus to qualifv for a further grant of 6000Z., 

 making a total of 12,000/., a sum which it is estimated 

 will give buildings and appliances adequate for some 

 years to come. 



THE GLASGOW MEETING OF THE 

 INSTITUTION OF NAVAL ARCHITECTS. 



THE Institution of Naval Architects held a suc- 

 cessful and largely attended summer meeting 

 in Glasgow on June 23-27. An interesting series of 

 visits to works and excursions had been arranged, 

 that to Messrs. Beardmore's shipyard, and the excur- 

 sion to Arran with which it was combined, proving 

 particularly enjoyable. While most of the papers 

 dealt with purely technical matters, one or two were 

 of more general interest. 



In a paper on safety of life at sea, Mr. Hillhouse 

 summed up the present state of affairs from the point 

 of view of the naval architect. Apart from careful 

 navigation the three factors on which we have to 

 rely are wireless telegraphy, subdivision of hulls, and 

 a sufficiency of boats. Of these, the adequate sub- 

 division of hulls presents very serious constructional 

 difficulties, and offers few advantages in the case of 

 lire, while it is almost impossible to provide sufficient 

 small boats and to guarantee that they shall all be 

 usable in the moment of emergency. The one thing 

 on which we can insist is careful navigation, although 

 this may involve some reduction in speed. 



Dr. S. J. P. Thearle directed attention to a number 

 of cases in which cracks have developed in the shell 

 plating of a steel vessel at points removed from rivet- 

 holes and from the edges of the plate. These have 

 been found to occur only in the vicinitv of a frame 

 unsupported by any beam, and are evidently due to 

 "fatigue" following alternate stressing of the plate 

 by " panting." 



In a paper on the effect of form and size on the 

 resistance of ships, Mr. J. S. Baker dealt with the 

 effect of an increase in the length of the parallel por- 

 tion of a vessel and of fullness of form. The problem 

 was first attacked from a theoretical point of view on 

 the assumption of stream-line flow ; the distribution of 

 pressure around the hull was computed ; and a law- 

 deduced for the speed at which transverse wave- 

 making" occurs. These results were compared with 

 those obtained from model experiments, and from 

 these 1 he author deduces an expression for the most 

 economic length of parallel body to be associated with 

 a given entrance and run. 



Prof. A. H. Gibson and Mr. Hannay Thompson 

 read a paper dealing with the theory of "suction," 

 or interaction between passing vessels, and with an 

 extensive series of experiments carried out to inves- 

 tigate this important question. The vessels used were 

 respectively 90 ft. and 30 ft. in length, displacing 

 respectively 96 and 26 tons. The experiments were 

 divided into two sets, one dealing with the behaviour 

 of the vessels when moving at different distances 

 apart and at different speeds with helms lashed amid- 

 ships, and the other dealing with the helm angles 

 NO. 2 2 7Q, VOL. qi] 



necessary to maintain a straight course and with the 

 forces and moments operative to produce deflection 

 of the course under similar conditions. The experi- 

 ments were carried out in deep and open water, and 

 the authors conclude that even in these circumstances 

 interaction is a very real danger to navigation under 

 certain conditions. The danger would appear to be 

 greatest when the larger vessel is passing the smaller 

 in fairly close proximity at a speed not greatlj in 

 excess of that of the smaller. In such circumstances, 

 particularly if the larger be at the time accelerating 

 with a view of drawing out of range of the smaller, 

 the latter may be drawn into collision, except in so far 

 as prevented by the helm, from distances as great as 

 three or four lengths of this vessel. With the vessels 

 within one length of each other the helm required 

 tip keep the smaller on its original course varied with 

 its longitudinal position relative to the larger, and 

 with their relative speeds. Whin all circumstances 

 favoured interaction a helm angle of as much as 20 

 was necessary to prevent collision. Generally speak- 

 ing, since the helm effect increases somewhat more 

 rapidly than that of suction, a vessel is more easily 

 controlled against these forces at high than at low 

 speeds. 



An interesting paper by Mr. A. Cannon records the 

 results of experiments with an apparatus designed bv 

 Sir H. Biles on principles laid down bv Colonel Russo, 

 R.I.N., to investigate the effect of internal loose 

 water upon the rolling of a ship amongst a regular 

 series of waves, while a paper by Mr. Lloyd Wood- 

 ward, dealing with the theory of the same subject, 

 forms a useful supplement to this. The experiments 

 point to the conclusion that, generally speaking, the 

 addition of free water decreases the angle of roll, 

 and always does so if its quantity is limited. If, 

 however, the quantity is fairly large, and particularly 

 in short and high waves, the effect is to increase the 

 angle, and under a certain combination of wave- 

 lengths and height the angle may become dangerous. 

 Further, these large angles are attained in a very 

 few rolls, and it is quite possible for them to be 

 attained in an actual ship, although the resistance to 

 roll may be very great. 



In a paper which was taken as read. Prof. L. 

 Gumbel dealt with the cavitation of screw propellers. 

 concluding that the tendency to cavitation not only 

 increases with a diminution in the depth of immersion 

 and with the amount of dissolved air in the water, 

 but also depends very largely on the pitch of the 

 propeller, on the angle formed by the feather edge in 

 the cross section of the blade, and on the amount of 

 slip. As regards the latter point, the limit of slip 

 which mav take place without cavitation is reduced 

 as til.- speed of the vessel increases. On the other 

 hand, the occurrence of cavitation is not dependent 

 on the surface pressure over the blade area. A small 

 angle at the emersion edge is more easily obtained 

 with a broad-bladed propeller than in one with nar- 

 rower blades. In this fact lay, in the author's 

 opinion, the secret of the success that had been ob- 

 tained with turbine screws with broad blades. Since, 

 however, broad blades involve increased friction, an 

 attempt should be made to so form the cross section 

 as to get a narrow blade with the minimum possible 

 ansrle of emersion. 



Other papers descriptive of the results of trials on 

 modern vessels propelled respectively by geared tur- 

 bines and bv Diesel engines enable an interesting 

 comparison to be gained between the performance of 

 these tvpes of motor. In the turbine installation of 

 2400 b.h.p. the steam consumption was only 1255 lb. 

 per shaft h.p., the ratio of effective h.p. to shaft h.p. 

 attaining a maximum value of about 58 per cent, at 



